Adult Ice Cream Dragon

Ice Walk. The dragon can move across and climb icy surfaces without needing to make an ability check. Additionally, Difficult Terrain composed of ice or snow doesn't cost it extra movement.

Heroes' Feast. The dragon can cast the Heroes' Feast spell at will. The feast is comprised specifically of food and drink you would find at an ice cream stand: Ice cream cones, popsicles, ice cream sandwiches, etc.

Legendary Resistance (3/Day, or 4/Day in Lair). If the dragon fails a saving throw, it can choose to succeed instead.

Multiattack. The dragon makes three Rend attacks. If the dragon is in its Cream Form it makes two Pseudopod attacks. 

Rend. Melee Attack Roll: +10 to hit, reach 10 ft. Hit: 12 (2d6 + 5) Slashing damage plus 5 (2d4) Cold damage.

Pseudopod (Cream Form Only). Melee Attack Roll: +10 to hit, reach 5ft. Hit: 12 (2d6 +5) Cold damage.

Ice Cream Breath (Recharge 5–6). Constitution Saving Throw: DC 18, each creature in a 60-foot Cone. Failure: 45 (10d8) Cold damage and its speed is halved until the end of its next turn. Success: Half damage.

Spellcasting. The dragon casts one of the following spells, requiring no Material components and using Charisma as the spellcasting ability (spell save DC 20, +12 to hit with spell attacks):

At Will: Detect Magic, Hold Monster, Ice Knife
1/Day Each: Ice Storm, Ice Wall

Cream Form. The dragon can alter itself to take on a form that is more akin to actual ice cream. In this form, the dragon is unaffected by Difficult Terrain, its speed becomes 30ft., can occupy occupied spaces, unaffected by the restrained, prone, and grappled condition, and takes up a 30ft radius circle of Difficult Terrain for any creature in it. The dragon cannot fly or make any Attack actions other than the Pseudopod attack. The dragon can transform back into its Draconic form by using a bonus action.

Legendary Action Uses: 3 (4 in Lair). Immediately after another creature's turn, the dragon can expend a use to take one of the following actions. The dragon regains all expended uses at the start of each of its turns.

Chill. The dragon uses Spellcasting to cast Hold Monster. The dragon can't take this action again until the start of its next turn.

Freezing Burst. Constitution Saving Throw: DC 12, each creature in a 30-foot-radius Sphere centered on a point the dragon can see within 120 feet. Failure: 3 (1d6) Cold damage, and the target's Speed is 0 until the end of the target's next turn. Failure or Success: The dragon can't take this action again until the start of its next turn.

Pounce. The dragon moves up to half its Speed, and it makes one Rend attack.